Single photon detection at near-infrared (NIR) wavelengths is critical for light detection and ranging (LiDAR) systems used in imaging technologies such as autonomous vehicle trackers and atmospheric remote sensing. Portable, high-performance LiDAR relies on silicon-based singlephoton avalanche diodes (SPADs) due to their extremely low dark count rate (DCR) and afterpulsing probability, but their operation wavelengths are typically limited up to 905 nm. Although InGaAs-InP SPADs offer an alternative platform to extend the operation wavelengths to eye-safe ranges, their high DCR and afterpulsing severely limit their commercial applications. Here we propose a new selective absorption and multiplication avalanche photodiode (SAM-APD) platform composed of vertical InGaAs-GaAs nanowire arrays for single photon detection. Among a total of 4400 nanowires constituting one photodiode, each avalanche event is confined in a single nanowire, which means that the avalanche volume and the number of filled traps can be drastically reduced in our approach. This leads to an extremely small afterpulsing probability compared with conventional InGaAs-based SPADs and enables operation in free-running mode. We show DCR below 10 Hz, due to reduced fill factor, with photon count rates of 7.8 MHz and timing jitter less than 113 ps, which suggest that nanowire-based NIR focal plane arrays for single photon detection can be designed without active quenching circuitry that severely restricts pixel density and portability in NIR commercial SPADs. Therefore, the proposed work based on vertical nanowires provides a new degree of freedom in designing avalanche photodetectors and could be a stepping stone for high-performance InGaAs SPADs.

Controlling the propagation and intensity of an optical signal is central to several technologies ranging from quantum communication to signal processing. These require a versatile class of functional materials with tailored electronic and optical properties, and compatibility with different platforms for electronics and optoelectronics. Here, the inherent optical anisotropy and mechanical flexibility of atomically thin semiconducting layers are investigated and exploited to induce a controlled enhancement of optical signals. This enhancement is achieved by straining and bending layers of the van der Waals crystal indium selenide (InSe) onto a periodic array of Si‐pillars. This enhancement has strong dependence on the layer thickness and is modelled by first‐principles electronic band structure theory, revealing the role of the symmetry of the atomic orbitals and light polarization dipole selection rules on the optical properties of the bent layers. The effects described in this paper are qualitatively different from those reported in other materials, such as transition metal dichalcogenides, and do not arise from a photonic cavity effect, as demonstrated before for other semiconductors. The findings on InSe offer a route to flexible nano‐photonics compatible with silicon electronics by exploiting the flexibility and anisotropic and wide spectral optical response of a 2D layered material.

Integration of ultracompact light sources on silicon platforms is regarded as a crucial requirement for various nanophotonic applications. In this work, InGaAs/InP core/shell nanowire array photonic crystal lasers are demonstrated on silicon‐on‐insulator substrates by selective‐area epitaxy. 9 × 9 square‐lattice nanowires forming photonic crystal cavities with a footprint of only 3.0 × 3.0 μm2, and a high Q factor of 23 000 are achieved by forming these nanowires on two‐dimensional silicon gratings. Room‐temperature lasing is observed from a fundamental band‐edge mode at 1290 nm, which is the O‐band of the telecommunication wavelength. Optimized growth templates and effective in‐situ passivation of InGaAs nanowires enable the nanowire array to lase at a low threshold of 200 μJ cm−2, without any signature of heating or degradation above the threshold. These results represent a meaningful step toward ultracompact and monolithic III–V lasers on silicon photonic platforms.

Monolithic integration of III-V nanowires on silicon platforms has been regarded as a promising building block for many on-chip optoelectronic, nanophotonic, and electronic applications. Although great advances have been made from fundamental material engineering to realizing functional devices, one of the remaining challenges for on-chip applications is that the growth direction of nanowires on Si(001) substrates is difficult to control. Here, we propose and demonstrate catalystfree selective-area epitaxy of nanowires on ( 001)-oriented silicon-on-insulator (SOI) substrates with the nanowires aligned to desired directions. This is enabled by exposing {111} planes on (001) substrates using wet chemical etching, followed by growing nanowires on the exposed planes. We demonstrate the formation of nanowire array-based bottom-up photonic crystal cavities on SOI(001) and their coupling to silicon waveguides and grating couplers, which support the feasibility for onchip photonic applications. The proposed method of integrating position-and orientationcontrollable nanowires on Si(001) provides a new degree of freedom in combining functional and ultracompact III-V devices with mature silicon platforms.

The back‐cover image represents lasing from square‐lattice nanowire array photonic crystals on silicon‐on‐insulator (SOI) platforms. Integration of light sources on silicon platforms is regarded as a crucial requirement for various nanophotonic applications, but the lattice mismatch between III–V materials and silicon has been one of the major challenges to realize this. Here, Hyunseok Kim et al. (article no. http://doi.wiley.com/10.1002/pssr.201800489) employed bottom‐up integrated nanowires to overcome this issue and realize highquality III.V materials on silicon. InGaAs/InP core/shell nanowires form photonic crystals with a footprint of only 3.0×3.0 μm2, and a high Q factor of 23,000 is achieved by integrating these nanowires on two‐dimensional silicon gratings. Roomtemperature lasing is observed from a fundamental band‐edge mode at 1290 nm, which is the O‐band of the telecommunication wavelength. These results represent a meaningful step toward ultracompact and monolithic III–V lasers on silicon photonic platforms.